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Distribution:

Hawaii Island and Kauai

Biology:

Natural History:

Wasmannia auropunctata is a pest ant about which much has been written (e.g., Clark et al. 1982, De Souza et al 1998, Fabres and Brown 1978, Jourdan 1997, Lubin 1984, Ulloa Chac?n and Cherix 1990, Williams 1994). The species is remarkably catholic in its habitat preference. It can be abundant in primary forest or young second growth, wet forest or dry forest, although it is perhaps most abundant in disturbed habitats. It can be an agricultural pest in many parts of the tropics because of its strong sting.

The sting of Wasmannia is worth commenting on. These are extremely tiny ants, barely visible in the field. When I first began studying ants in Costa Rica, for a while I was puzzled about Wasmannia. By literature and reputation Wasmannia was reputed to have a terrible sting, but I had been collecting them for months in Corcovado National Park and never experienced the famous sting. Then one day I was collecting from a populous nest and some workers made it up to the soft skin of my inner forearm and began to sting. The sting was not terrible, about as bad as a fire ant (i.e., Solenopsis geminata) but inordinately strong for an ant you could barely see! I then learned that they are so small they cannot sting through the thicker skin of your hands. I subsequently learned that necks are nice places to get stung. Often when crawling through trashy second growth or Heliconia thickets my neck would start to burn. I would reach around to find the culprit and find nothing there. This was my cue that it was Wasmannia, and often a close inspection would reveal that I had brushed into a nest and workers were scattered on my head and shoulders.

Colonies are polygynous and it is never clear where colony boundaries are. Dozens of dealate queens may be found together in nests. Nests can be almost anywhere: in rolled leaves or dead sticks in the leaf litter, under stones, in rotten wood, in hollow stems suspended above the ground, in ant-plant domatia, and under epiphytes. Workers are omnivorous scavengers and predators and can rapidly recruit to food.

Longino, J. T., 2007:
Taxonomic comments
Workers of W. auropunctata have a strongly quadrate petiolar node. The anterior face of the node is sharply differentiated from both the peduncle and the dorsal face of the node, meeting both at nearly right angles, and forming a strongly step-like profile. This is a highly distinctive feature that easily distinguishes auropunctata workers from all other Wasmannia species. Within the species there is abundant variation in the strength of sculpturing and coloration, and this has engendered the naming of nine infraspecific forms in addition to the nominotypical. We have never been able to discover evidence of discrete forms among the workers of auropunctata , either in sympatry or allopatry; the variation appears continuous. Three of the forms have already been synonymized by others: atomum , glabra , and panamana . We have been able to examine types of three additional forms — obscura , pulla , and rugosa — and they fall well within our concept of auropunctata . The remaining forms — australis , laevifrons , nigricans — we have not examined, but the published descriptions give no indication that they are beyond the range of variation of auropunctata . We have synonymized them, following the philosophy that taxa should be synonymized unless evidence of distinctness is obtained.
The above synonymy does not assure that there is no genetic structuring, and perhaps species-level differences, within the broad concept of auropunctata . There may even be distinct sympatric species. In Costa Rica, there appear to be two size classes of queens (Fig. 2). Queens with smaller heads include ten from various sites in Costa Rica, including La Selva Biological Station and the Penas Blancas Valley, one from Jamaica, and one from Venezuela. Queens with large heads are all from the Atlantic slope of Costa Rica. Three are from La Selva (two from different Winkler samples of sifted leaf litter from the forest floor, one from a small nest under an epiphyte mat in an old treefall) and one is an alate queen found in a Cecropia sapling near Volcan Arenal. Thus the small-headed and big-headed forms are broadly sympatric in Costa Rica. Among the small-headed queens four are definitively associated with workers from the same colony, and among the big-headed queens one is associated with workers. Others have workers doubtfully associated (together in the same Winkler sample). We can discern no differences in workers associated with the two types of queens. The cause of the two size classes of queens is unknown, but could reflect either differences between cryptic species or intraspecific polymorphism.
An aberrant worker form is frequently encountered in large samples of W. auropunctata . These aberrant workers have the head grossly swollen. The entire head is more spherical than normal, as if the head were inflated like a balloon. The rest of the body is little different from a normal worker. These aberrant workers are occasionally encountered in Winkler samples that contain hundreds or thousands of auropunctata workers.
Natural History
Wasmannia auropunctata is a widespread pest ant (Clark et al., 1982; De Souza et al., 1998; Fabres & Brown, 1978; Jourdan, 1997; Lubin, 1984; Ulloa Chacon & Cherix, 1990; Williams, 1994; Wetterer & Porter, 2003). In its presumed native range it occurs from Argentina to Mexico (Kempf, 1972; Wetterer & Porter, 2003). Its introduced range includes the Galapagos Islands, West Africa (Gabon, Cameroon, and possibly the Republic of Congo and the Democratic RepubIic of Congo), Melanesia (New Caledonia, Solomon Islands, Vanuatu, and possibly Tuvalu), Polynesia (Wallis and Futuna and Hawaii), parts of the US (Florida and possibly California), and subtropical Atlantic islands (the Bahamas and Bermuda) (Wetterer & Porter, 2003). It is widespread on Caribbean islands, but it is unclear whether these are long-term native populations or recent introductions (Wetterer & Porter, 2003).
The species is remarkably catholic in its habitat preference. It is common in habitats ranging from wet to dry and from early successional to mature. In an elevational gradient of mature wet forest on the Atlantic slope of Costa Rica (the Barva Transect, from La Selva Biological Station to 2000 m elevation on the slope of Volcan Barva) it is abundant at 50 m and 500 m elevations, but nearly absent at 1070 m (Table 2). In the lowland habitats where it is abundant, it occurs in leaf litter on the forest floor and at all levels in the vegetation.
Although it occurs frequently in samples from mature forest habitats in Costa Rica, it is never so abundant in those habitats that it is noticeable as a pest or appears to be displacing other native species (Tennant, 1994; McGlynn & Kirksey, 2000; pers. obs.). In contrast, in certain agricultural habitats (banana plantations) and in parts of the tropics where it has been introduced it becomes super-abundant, with negative impacts on native species and human comfort (Clark et al., 1982; Wetterer & Porter, 2003). In dry-forest fragments in Colombia there is a negative correlation between W. auropunctata abundance and overall ant diversity (Armbrecht & Ulloa Chacon, 2003). Where introduced in New Caledonia it invades dense native forest and displaces native ants (Le Breton et al., 2003). Behavioral tests and cuticular hydrocarbon analysis show that W. auropunctata is multicolonial in its native range in Brazil, unicolonial where introduced in New Caledonia (Errard et al., 2002).
The sting of Wasmannia is noteworthy. These are extremely tiny ants, barely visible in the field. When the senior author first began studying ants in Costa Rica, he was at first puzzled about Wasmannia . By literature accounts Wasmannia was reputed to have a terrible sting, but he had been collecting them for months in Corcovado National Park without ever experiencing the famous sting. One day he was collecting from a populous nest and some workers made it up to the soft skin of his inner forearm and began to sting. The sting was definitely noticeable, about as severe as a fire ant (i. e., Solenopsis geminata ) but inordinately strong for an ant that could barely be seen! Workers are so small they cannot sting through the thicker skin of the hands.
Surprisingly, the chemical and toxicological nature of the venom of W. auropunctata has not been investigated. Howard et al. (1982) discovered an alkylpyrazine compound in the mandibular glands, which acted as an attractant to conspecifics and a repellent to heterospecifics. They speculated that the workers might apply the mandibular gland product as an irritating secretion, augmenting the defensive properties of the venomous sting. It would be interesting to investigate whether the venom alone is the powerful agent in this small ant, or if the strong burning sensation is a synergetic effect of venom plus mandibular gland product.
Nests can be almost anywhere: in rolled leaves or dead sticks in the leaf litter, under stones, in rotten wood, in hollow stems suspended above the ground, in ant-plant domatia, and under epiphytes. Workers are omnivorous scavengers and predators and can rapidly recruit to food. Colonies are polygynous and it is never clear where colony boundaries are. Dozens of dealate queens may be found together in nests. Males are rare but do occasionally occur.

Specimen Habitat Summary

Found most commonly in these habitats: 837 times found in mature wet forest, 400 times found in montane wet forest, 343 times found in tropical rainforest, 264 times found in tropical moist forest, 246 times found in 2º lowland rainforest, 242 times found in ridgetop cloud forest, 230 times found in 2º wet forest, 225 times found in lowland wet forest, 150 times found in tropical wet forest, 114 times found in mesophil forest, ...

Collected most commonly using these methods or in the following microhabitats: 1751 times MiniWinkler, 989 times Baiting, 245 times Winkler, 178 times Mini Winkler, 91 times Berlese, 134 times MaxiWinkler, 73 times Malaise, 50 times search, 36 times Fogging, 50 times Sweeping, 32 times Beating, ...

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